Photo
Study Of A Leucistic Red-tailed Hawk And Other Raptors In Montgomery and Bucks
County, PA, February 1st, 2013

August
Mirabella and I took a drive for a couple of hours through Montgomery and Bucks
Counties today. We were rewarded with ten
different Red-tailed Hawks. But the most interesting sight was a leucistic,
mostly white,
adult Red-tailed Hawk with dark eyes, yellow beak and legs, and
a few normally colored
primary and tail feathers. Here are some photos
of this neat bird.

And
for comparative purposes, here is a photo of another leucistic Red-tailed
Hawk taken at Cape May State Park, November 3rd, 2010

A
Tannish Colored Leucistic Red-tailed Hawk At Cape May State Park In 2010

And
A Normally Hued Juvenile Red-tailed Hawk At Nockamixon State Park
Today

In any event, leucism is
unusual in birds but not rare. Interestingly, albinism only applies to a total
absence of melanin. Since some colors come from other pigments, such as
carotenoids, it is possible for a bird to be albinistic
and still have color. Leucism, on the other hand, applies to all pigments. It is also possible for a bird to be completely white and still have melanin in the body. In this case, the
bird would be considered leucistic and would have dark eyes because the
mutation only applies to depositing melanin in the feathers. Albinistic birds have pink eyes because
without melanin in the body, the only color in the eyes comes from the blood
vessels behind the eyes. And since leucism is a deposition problem, it makes sense that birds
with white patches would be leucistic. Consequently leucism comes in two main
varieties, paleness, an equal reduction of melanin in all feathers; and pied, an absence of
melanin in some feathers creating white patches. (Cornell BNA; Wikipedia; Sibley Guide To Birds)